Domain-Driven Data at SunshinePHP

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Open for Data Dome (outside) by Bradley Holt.

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Brent Spiner with Zoltar from Big by Bradley Holt, on Twitter . Big Data

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IBM Cloud / February 9, 2018 / © 2018 IBM Corporation The Relational Database order *order_id customer_id date customer line_item *customer_id email_address name *order_id *item_id price quantity database 2 by Tim Morgan, on Flickr (CC BY 2.0).

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The ACID guarantees provided by relational databases were (and often still are) critical for systems of record IBM Cloud / February 9, 2018 / © 2018 IBM Corporation IBM 360 Announcement center by Robert Nix, on Flickr (CC BY 2.0).

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The introduction of the Web brought new types of applications with different constraints than systems of record IBM Cloud / February 9, 2018 / © 2018 IBM Corporation Dialing Up Web History by Mike Licht, on Flickr (CC BY 2.0).

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The introduction of mobile apps added to the growing number of systems of engagement IBM Cloud / February 9, 2018 / © 2018 IBM Corporation Instagram and other Social Media Apps by Jason Howie, on Flickr (CC BY 2.0).

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Every node in an eventually consistent distributed system will eventually arrive at a consistent state if given no new updates IBM Cloud / February 9, 2018 / © 2018 IBM Corporation Spider Web by Alden Chadwick, on Flickr (CC BY 2.0).

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IBM Cloud / February 9, 2018 / © 2018 IBM Corporation Domain Layer Order Aggregate «interface» OrderRepository + insertOrder(order:Order) + updateOrder(order:Order) + findOrderById(id:int) : Order + recentOrders([limit:int]) : Order[0..*] Customer … Infrastructure Layer LineItem … Order - id : int - customer : Customer - date : Date - lineItems : LineItem[1..*] + total() : Money InMemoryOrderRepository + insertOrder(order:Order) + updateOrder(order:Order) + findOrderById(id:int) : Order + recentOrders(limit:int) : Order[0..*] RelationalMapperOrderRepository + insertOrder(order:Order) + updateOrder(order:Order) + findOrderById(id:int) : Order + recentOrders(limit:int) : Order[0..*]

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Object-oriented programming and relational databases use different models, resuting in the object-relational impedance mismatch IBM Cloud / February 9, 2018 / © 2018 IBM Corporation Financial District Classical Building Reflection Distortion, San Francisco, California, USA by Wonderlane, on Flickr (CC BY 2.0).

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“This is the world of NoSQL to me, that we can choose a tool that fits well with the problem we’re trying to solve.” Eric Evans (author of Domain-Driven Design) Software Engineering Radio Episode 226: Eric Evans on Domain-Driven Design at 10 Years, 2015 IBM Cloud / February 9, 2018 / © 2018 IBM Corporation http://www.se-radio.net/2015/05/se-radio-episode-226-eric-evans-on-domain-driven-design-at-10-years/

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Each bounded context should have its own data layer, and should not directly access a data layer belonging to a different bounded context IBM Cloud / February 9, 2018 / © 2018 IBM Corporation Hexagons by Henry Burrows, on Flickr (CC BY-SA 2.0).

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A data layer may be a database, or it can be a data system consisting of multiple databases— sometimes called polyglot persistence IBM Cloud / February 9, 2018 / © 2018 IBM Corporation FLOWERS Mixed Boquet by kazandrew, on Flickr (CC BY-SA 2.0).

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IBM Cloud / February 9, 2018 / © 2018 IBM Corporation Catalog Document Database Key/Value Store Graph Database Full Text Search Shopping Cart Document Database Key/Value Store Orders Relational Database Big Data Analytics

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Rather than update an entity in place, Command Query Responsibility Segregation (CQRS) provides separate read and write models IBM Cloud / February 9, 2018 / © 2018 IBM Corporation rectangles-10 by Karen Cropper, on Flickr (CC BY 2.0).

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IBM Cloud / February 9, 2018 / © 2018 IBM Corporation Domain Layer Read Model «interface» OrderQueryHandler + findOrderById(id:int) : OrderDetails + recentOrders([limit:int]) : OrderSummary[0..*] Write Model OrderDetails + getId() : int + getCustomer() : Customer + getDate() : Date + getLineItems() : LineItem[1..*] + getTotal() : Money «interface» OrderCommandHandler + handle(command:CreateOrder) + handle(command:AddLineItem) CreateOrder - customer : Customer - date : Date - lineItems : LineItem[1..*] OrderSummary + getId() : int + getDate() : Date + getTotal() : Money AddLineItem - orderId : int - lineItem : LineItem

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Event sourcing is an architecture in which application state is computed from a sequence of events IBM Cloud / February 9, 2018 / © 2018 IBM Corporation Rusty Chain by veggiefrog, on Flickr (CC BY 2.0).